For industries which rely heavily upon mechanical assets, extensive maintenance strategies are essential.
There are three main forms of maintenance philosophy; Breakdown maintenance (fixing machinery following a break-down), Preventative maintenance (undertaking maintenance tasks after a certain time period) and predictive or condition-based maintenance (understanding the machinery health and basing maintenance on its condition).
In this blog post, we are going to look into vibration condition monitoring, which is a form of condition-based maintenance. As machinery ages and wears, vibration levels and signatures change – this can be a very useful tool to predict when failures are likely to occur and also allows us to diagnose faults using non-destructive analysis.
The measurement methodology is fairly straight-forward. A vibration sensor (usually an accelerometer) is attached to the machine under assessment in close proximity to the machine bearings where possible. The bearings are generally the best measurement location as this is the ‘bridging point’ where mechanical vibrations transfer most efficiently. A measurement of vibration levels is then taken with a suitable vibration measurement system (calibrated to UKAS standards in the case of NCSL) and compared to reference vibration levels for various categories of machines.
A machinery health diagnosis can then be formed, and maintenance can be undertaken if required.
Furthermore, regular assessment allows for a trend analysis to be conducted. In some cases, this can be much more valuable than the absolute vibration level, as a degrading trend can indicate issues, even if the vibration level is not excessive. On the other hand, a high level of vibration may not be a cause for alarm if the trend is stable and the acceleration levels are not increasing over time.
To further build upon this technique, diagnostic methods can be used to understand the cause of high vibration levels without the need for down-time or disassembling machinery. NCSL techniques can be used to identify:
- Unbalance of rotating parts
- Misalignment of couplings and bearings
- Bent shafts
- Worn or damaged gears and bearings
- Bad drive belts and chains
- Torque variations
- Electromagnetic forces
- Aerodynamic forces
- Hydraulic forces
This is possible by the measurement and analysis of multiple time-synchronised vibration signals from the machinery under assessment.
Many industries already incorporate vibration measurement into their maintenance schedule, however this is usually far from comprehensive. Measurements are often undertaken using hand-held monitors, this is inherently inaccurate, as the probe angle and probe pressure can lead to huge variance in measured vibration levels. These types of devices are often not calibrated and therefore readings taken should be treated with caution.
In addition to vibration condition monitoring services, NCSL can also use acoustic measurement methods to understand machinery condition. As vibration levels increase, and machinery defects occur, noise emission from mechanical devices will also change. As an expert acoustic consultancy, NCSL can also provide this service to our clients.
In summary, the introduction of a vibration condition-monitoring maintenance program offers a vast number of advantages, such as:
- An increase in machine productivity
- Extended intervals between overhauls
- Minimise the number of ‘open, inspect and repair if necessary’ routines
- Improve repair time
- Increase machine life
- Resources for repair can be properly planned
- Improve product quality
- Save on maintenance costs
If you are interested in the advantages above and would like to book a measurement appointment with NCSL, please feel free to contact us.